1. Field of the Invention
This invention relates in general to covers for the bed of a pickup truck and more particularly to a vertically extensible cover assembly having a lowered position for secured containment of articles in the bed of a pickup truck and an elevated position which permits carrying relatively large articles therein.
2. Description of the Prior Art
The prior art is replete with covers for pickup truck beds ranging from canvas-like covers held in place by snaps to considerably more expensive and complex covers such as a rigid molded plastic cover which is hinged at the front end of the bed. The various types of covers all have some drawbacks. For example, the canvas-like covers mentioned above, sometimes referred to as a tonneau covers, provide virtually no security for articles contained in the bed other than hiding them from view. Also, the only way that relatively large articles, e.g. those which stick up above the sides of the bed, can be carried in a pickup bed that is equipped with a tonneau cover is to remove the cover. The hinged plastic cover provides the desired security but does not make any provisions for carrying large objects.
A particular prior art cover assembly is fully disclosed in U.S. Pat. No. 3,675,885. The cover is a rigid structure which is attached by four special spring-loaded arms located at the corners of the bed of a pickup truck. The arms are designed to fold inwardly relative to the bed of the pickup truck and when all four arms are folded inwardly, the cover will be in its lowered position wherein it will be in resting engagement with the upper ledges of the bed and the cover is provided with means for being locked in its lowered position. By lifting one side or the other of the cover so as to unfold the two arms on the lifted side, the cover will be moved into a tilted partially elevated position so that access to the contents of the pickup bed can be obtained from either side thereof. When both sides of the cover are lifted so as to unfold all four arms, the cover will, of course, be in the fully elevated position and this provides sufficient clearance for virtually any large objects. When the cover is fully elevated, the arms may be locked in their unfolded extended states to allow the pickup to be driven with the cover elevated.
This particular prior art structure is, however, not without some drawbacks. As mentioned above, the folding arms are spring-loaded, and those springs provide the counter-balancing forces needed to help in raising the cover. When the arms are in their folded positions, the counter-balancing springs are stretched taut and folded over the ends of the arms at pivotably interconnected junction, or joint, or legs of the arms. The pivotably interconnected legs are configured so that they provide a relatively sharp edge at the pivot joint and the springs become stretched or otherwise distorted at the location where they engage the pivot joint. Therefore, the counter-balancing springs lose some of their load counter-balancing capability.
The means for locking the folding arms in their extended unfolded positions is in the form of pull pins which are slidably inserted into aligned holes formed through the overlapped ends of the pivotably interconnected legs of each of the folding arms. Sometimes vehicular vibrations cause the pull pins to back out of the aligned holes and this problem is aggravated when the trucks are operated on bumpy roads.
Attachment of the lower ends of the folding arm to the upper ledges of the pickup bed is accomplished by a pair of right angle brackets which are bolted on the upper ledges of the bed. These brackets are difficult to mount on the pickup bed so as to be in proper alignment and they can become mis-aligned in use. Also, the brackets are not readily adaptable for being mounted in various attitudes to accommodate the various configurations of pickup beds being manufactured today.
This prior art structure was disclosed in the above mentioned U.S. Patent as having a stabilizing bar associated with each of the folding arms for stabilizing the cover in a direction coincident with the longitudinal dimension of the vehicle when being driven with the cover in the elevated position. The disclosed longitudinal stabilizing bars are rigid and extend from the pivot joint of their respective arms and are attached to the upper ledges of the pickup bed. The attachment of the stabilizing arms to the ledges of the bed is in the form of a pivot connection so that the stabilizing bars will pivot inwardly with the folding arms when the arms are folded to lower the cover. In use, it was found that the stabilizing bars were not needed in that longitudinal stabilization was not the problem. In that the folding arms must be capable of folding inwardly relative to the pickup truck bed, the cover is inherently unstable in the transverse direction relative to the longitudinal dimension of the pickup truck and not in the longitudinal direction.
Therefore, a need exists for a new and improved cover assembly for use on the bed of a pickup truck with the cover assembly overcoming some of the shortcomings of the prior art.